This invention relates to improvements to waterproofing materials which are in the form of pre-formed, sheet-like laminates of (a) a waterproof and waterproofing bituminous membrane adhered to (b) a support sheet material covering at least one major surface of the bituminous membrane.
It is known that structural surfaces and the like such as concrete decks, foundations, roofs, etc., can be sealed in a waterproof manner by forming thereon a continuous membrane of a bituminous composition which is substantially impermeable to moisture. The term "bituminous composition" as used in the present disclosure refers to compositions based on tar, asphalt or pitch with or without added components. In the past such waterproofing membranes have been formed by "in situ" application of a hot bituminous composition or of a cold solution or emulsion of bitumen, tar or pitch, typically in combination with one or more "plys" of bitumen-saturated felts. These known methods of "in situ" application of adhesive and felts suffer serious disadvantages. The procedures require the formation of a layer of waterproofing sealant at the job site which does not permit the assurance of a uniform application or of a resultant uniform layer. In addition, such application causes additional expenses of labor at the job site. Finally, application of such waterproofing to vertical substructural membranes is both tedious and in certain instances unmanageable.
More recently, waterproofing of structural surfaces has been accomplished by the application of pre-formed, flexible membranes of bituminous compositions which are pressure sensitive-adhesive such as those disclosed in U.S. Pat. Nos. 3,741,856; 3,853,682 and 3,900,102 to John Hurst. These waterproofing materials have a laminate structure comprising a sheet-like support member such as a polymer film adhered to a membrane of a flexible bituminous composition superimposed thereon. The bituminous composition may be single or multilayered and has self-adhesive properties which render it adherent to the support sheet and also to the substrate surface to which it is applied.
Generally, the known pre-formed self-adhered waterproofing structures of the foregoing type have a support sheet such as polymer film and a membrane of bituminous composition which are essentially co-extensive and, in addition, have a removable protective or release sheet positioned on the free surface of the adhesive membrane which must be removed before application of the waterproofing laminate to the structural surface. Pre-formed waterproofing laminates of each type have also been formed with the membrane of bituminous composition extending a short distance beyond the support sheet to yield a partially exposed surface. These partially exposed surfaces aid in forming watertight joints at overlaps of successively-applied laminates.
Pre-formed waterproofing laminates comprised of polymer film layers and bituminous waterproofing membranes and which are not self-adhesive to the substrate are also known. For example, a pre-manufactured membrane laminate product "KMM" described in a product brochure entitled "KMM Koppers Roofing and Waterproofing Membrane", published by Koppers Company, Inc., 1976, is a non-self adhesive, multi-layer laminate comprised of several layers of plastic film and bitumen composition which is laid upon a substrate and thereafter abutting edges of like laminates are heated to "weld" the laminates into a continuous waterproofing layer non-adherent to the substrate. Also, in U.S. Pat. No. 4,039,706 to Tajima Roofing Co. Ltd., self-adhesive strip-laminates comprised of a sheet support and self-adhesive bituminous layers are said in one embodiment to be applicable to roofs, etc., adhesive-side up. Another like laminate is then applied adhesive-side down to the upper exposed layer of adhesive of the first applied laminate resulting in a continuous waterproofing membrane layer composed over its entirety of "multi-layers" of bituminous adhesive and sheet support.
A drawback inherent in all of the aforementioned types of pre-formed waterproofing laminates is that the support sheets for the bituminous membranes often used therein can sometimes be adversely affected by oils present in the bituminous composition. For example, the dimensional stability of polyethylene film, a popular support sheet often used in such pre-manufactured waterproofing membranes, can be adversely affected when the film is contacted by oils such as aromatic oils present in the bituminous composition. A decrease in the dimensional stability of the polymer film by prolonged contact with such oils can lead to undesirable curling of the applied laminate upon exposure to elevated temperature.